Apparatus for and method of reducing power consumption in a cable modem

ABSTRACT

A novel apparatus and method of reduced power consumption for battery backup operation of a communication device such as a cable modem. When the cable modem senses a failure of the external power source it requests from the cable head-end to switch from multi-channel DOCSIS 3.0 operation to single-channel DOCSIS 2.0 operation. In response to approval by the cable head-end, the cable modem shuts down multi-channel circuits in the PHY such as the wideband analog to digital converter (ADC) which is normally used during multi-channel operation. In its place, it activates narrowband circuitry such as a narrowband ADC which consumes far less power. Tuner filter circuits are also swapped to match the reduced bandwidth requirements of battery backup operation. To further reduce power, the narrower bandwidth requirements during battery backup operation permit the linearity of a programmable gain amplifier (PGA) in the upstream path to be reduced.

REFERENCE TO PRIORITY APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 60/807,736, filed Jul. 19, 2006, entitled “Method and Apparatus toLower Power Consumption During Battery usage Situation”, incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of data communications andmore particularly relates to an apparatus for and method of reducing thepower consumption of a cable modem.

BACKGROUND OF THE INVENTION

Currently there are more than 50 million high-speed Internet accesscustomers in North America. Recently, the cable modem has become thebroadband connection of choice for many Internet users, being preferredover the nearest rival broadband technology, Digital Subscriber Line(DSL), by a significant margin.

Cable modems are well known in the art. A cable modem is a type of modemthat provides access to a data signal sent over the cable television(CATV) infrastructure. Cable modems are primarily used to deliverbroadband Internet access, taking advantage of unused bandwidth on acable television network. In 2005 there were over 22.5 million cablemodem users in the United States alone.

A cable modem is a network appliance that enables high speed dataconnections to the internet via data services provided by the localcable company. Data from the home is sent upstream on a carrier thatoperates on the 5 MHz to 42 MHz band of the cable spectrum. Downstreamdata is carried on a 88 MHz to 860 MHz band. The cable modem system canhave additional networking features such as Voice over IP (VoIP),wireless connectivity or network switch or hub functionality.

The term cable Internet access refers to the delivery of Internetservice over the cable television infrastructure. The proliferation ofcable modems, along with DSL technology, has enabled broadband Internetaccess in many countries. The bandwidth of cable modem service typicallyranges fro 3 Mbps up to 40 Mbps or more. The upstream bandwidth onresidential cable modem service usually ranges from 384 kbps to 30 Mbpsor more. In comparison, DSL tends to offer less speed and more variancebetween service packages and prices. Service quality is also far moredependent on the client's location in relation to the telephonecompany's nearest central office or Remote Terminal.

Users in a neighborhood share the available bandwidth provided by asingle coaxial cable line. Therefore, connection speed varies dependingon how many people are using the service at the same time. In most areasthis has been eliminated due to redundancy and fiber networks.

With the advent of Voice over IP telephony, cable modems are also beused to provide telephone service. Many people who have cable modemshave opted to eliminate their Plain Old Telephone Service (POTS). Analternative to cable modems is the Embedded Multimedia Terminal Adapter(EMTA). An EMTA allows multiple service operators (MSOs) to offer bothHigh Speed Internet and VoIP through a single piece of customer premiseequipment. A multiple system operator is an operator of multiple cabletelevision systems.

Many cable companies have launched Voice over Internet Protocol (VoIP)phone service, or digital phone service, providing consumers a truealternative to standard telephone service. Digital phone service takesthe analog audio signals and converts them to digital data that can betransmitted over the hybrid fiber coaxial (HFC) network of the cablecompany. Cable digital phone service is currently available to themajority of U.S. homes with a large number of homes are now subscribing.The number of homes subscribing is currently growing by hundreds ofthousands each quarter. One significant benefit of digital phone serviceis the substantial consumer savings, with one recent study sayingresidential cable telephone consumers could save an average of $135 ormore each year.

The Data Over Cable Service Interface Specification (DOCSIS) compliantcable modems have been fueling the transition of cable televisionoperators from a traditional core business of entertainment programmingto a position as full-service providers of video, voice, and datatelecommunications services.

The latest DOCSIS specification, DOCSIS 3.0, include a number ofenhancements, most notably, channel bonding and support for IPv6.Channel bonding provides cable operators with a flexible way to increaseupstream and downstream throughput to customers, with data rates in thehundreds of megabits and potentially gigabits per second. DOCSIS 3.0increases the capacity of cable modems to a minimum of 160 Mbpsdownstream to customers and to a minimum of 120 Mbps upstream.

Cable systems transmit digital data signals over radio frequency (RF)carrier signals. To provide two-way communication, one carrier signalcarries data in the downstream direction from the cable network to thecustomer and another carrier signal carries data in the upstreamdirection from the customer to the cable network. Cable modems aredevices located at the subscriber premises that functions to convertdigital information into a modulated RF signal in the upstreamdirection, and to convert the RF signals to digital information in thedownstream direction. A cable modem termination system (CMTS) performsthe opposite operation for multiple subscribers at the cable operator'shead-end.

Typically, several hundreds of users share a 6 MHz downstream channeland one or more upstream channels. The downstream channel occupies thespace of a single television transmission channel in the cableoperator's channel lineup. It is compatible with digital set top MPEGtransport stream modulation (64 or 256 QAM), and provides up to 40 Mbps.A media access control (MAC) layer coordinates shared access to theupstream bandwidth.

In order to provide faster data rates to customers, DOCSIS 3.0introduces the concept of bonding several physical downstream channelsinto one virtual high speed pipe. Channel bonding is a load-sharingtechnique for logically combining multiple DOCSIS channels. DOCSIS 3.0defines channel bonding for both the upstream and downstream directions.For downstream channel bonding, each downstream DOCSIS channel carries apayload of approximately 38 Mbps (50 Mbps with EuroDOCSIS). Load sharingtraffic across multiple channels allows a maximum throughput of up toN×38 Mbps (or N×50 Mbps), with N representing the number of channelsbeing bonded. A separate 6 MHz or 8 MHz frequency is used for each ofthe bonded channels. Upstream channel bonding is possible for a minimumof four channels, 10 to 30 Mbps each, for a total of 40 to 120 Mbps ofshared throughput.

Cable modems and DOCSIS standard have made delivery of digital servicesover hybrid fiber coaxial (HFC) cable television systems possible.Digital data delivery of Internet data, video on demand movies,telephony, telephony over the Internet, interactive games, upstreamdelivery of security camera digital photos to security services and ahost of other applications is now possible. These services andapplications are useful and valuable with some requiring more bandwidththan others. Video and movies, for example, even when compressed usingMPEG standards, require large amounts of bandwidth.

The high speed and bandwidth requirements of these applications createdemands on the power consumption of user equipment. Power consumption,however, is normally not a major concern considering that most cablemodem boxes are connected to AC mains utility power. In general, a powerfailure is not considered a critical event as televisions and computersare not likely to be operating. Regarding telephony, however, regulatorybodies in some countries require the telephone network to operate evenin the event of a power failure. Thus, cable modems that providetelephony features in addition to Internet, video and other dataservices, must continue to operate for a certain duration of time (e.g.,8 hours) in the event of a power failure. Power for such continuedoperation is typically provided from a battery.

Thus, there is a need for a mechanism that is capable of lowering thepower consumption of cable modem equipment during battery backup mode ofoperation so as to maximize operating time of the telephony features.

SUMMARY OF THE INVENTION

The present invention is a novel apparatus and method of reducing thepower consumption of a communications device such as a cable modem. Thereduced power consumption mechanism of the present invention isapplicable to communication systems wherein it is desirable tosignificantly reduce power consumption during battery operation. Themechanism is particularly suitable for use in cable systems adapted toimplement the DOCSIS 3.0 specification which permits the fallback of thecable modem to DOCSIS 2.0 operation whereby operation switches frommulti-channel (i.e. DOCSIS 3.0) to single-channel (i.e. DOCSIS 2.0)operation.

When the cable modem senses a failure of the external power source itrequests from the cable head-end to switch from multi-channel DOCSIS 3.0operation to single-channel DOCSIS 2.0 operation. In response toapproval by the cable head-end, the cable modem shuts down multi-channelcircuits in the PHY such as the wideband analog to digital converter(ADC) which is normally used during multi-channel operation. In itsplace, it activates narrowband circuitry such as a narrowband ADC whichconsumes far less power. Tuner filter circuits are also swapped to matchthe reduced bandwidth requirements of battery backup operation. Tofurther reduce power, the narrower bandwidth requirements during batterybackup operation permit the linearity of a programmable gain amplifier(PGA) in the upstream path to be reduced by decreasing its current draw.

To aid in understanding the principles of the present invention, thedescription is provided in the context of a DOCSIS 3.0 capable cablesystem comprising a cable modem adapted to receive an RF feed from acable head-end (i.e. CMTS) and to distribute video, Internet andtelephony to a subscriber premises. It is appreciated, however, that theinvention is not limited to use with any particular communication deviceor standard and may be used in optical, wired and wireless applications.Further, the invention is not limited to use with a specific technologybut is applicable to any situation where it is desired to reduce thepower consumption during battery operation of the device.

Several advantages of the reduced power consumption mechanism include(1) the mechanism enables usage of a single wideband tuner and a singlewide band ADC during normal operation in contrast with prior artsolutions that require several narrow band tuners and ADCs requiringmuch higher power consumption; (2) during battery backup mode operation,the wideband ADC, which has higher power consumption, is shut down and anarrowband ADC is activated.

Note that many aspects of the invention described herein may beconstructed as software objects that are executed in embedded devices asfirmware, software objects that are executed as part of a softwareapplication on either an embedded or non-embedded computer systemrunning a real-time operating system such as WinCE, Symbian, OSE,Embedded LINUX, etc. or non-real time operating system such as Windows,UNIX, LINUX, etc., or as soft core realized HDL circuits embodied in anApplication Specific Integrated Circuit (ASIC) or Field ProgrammableGate Array (FPGA), or as functionally equivalent discrete hardwarecomponents.

There is thus provided in accordance with the invention, a method ofreducing power consumption in a cable modem coupled to a cable head-endand incorporating a PHY circuit having a normally active multi-channelwideband mode and single-channel narrowband mode of operation, themethod comprising the steps of sensing loss of external power to thecable modem, requesting from the cable head-end to switch to thesingle-channel narrowband mode of operation and upon approval from thecable head-end, shutting down the multi-channel wideband mode ofoperation and activating the single-channel narrowband mode ofoperation.

There is also provided in accordance with the invention, an apparatusfor reducing power consumption in a cable modem coupled to a cable modemtermination service (CMTS) comprising a power supply control circuitcoupled to an external power source and a battery, the power supplycontrol circuit operative to sense a failure of the external powersource and switch to battery backup, an analog front end (AFE) circuitcomprising a wideband analog to digital converter (ADC) and a narrowbandADC and a wideband/narrowband (WB/NB) control circuit operative toreceive an indication of a loss of external power from the power supplycircuit and to shut down the wideband ADC and activate the narrowbandADC in response thereto.

There is further provided in accordance with the invention, a method ofreducing power consumption in a cable modem coupled to a cable head-endand incorporating a PHY circuit having a normally active multi-channelwideband mode and single-channel narrowband mode of operation, themethod comprising the steps of switching from the multi-channel widebandmode of operation to the single-channel narrowband mode of operation inresponse to sensing a loss of external power to the cable modem andswitching from the single-channel narrowband mode of operation back tothe multi-channel wideband mode of operation in response to sensing therestoration of external power to the cable modem.

There is also provided in accordance with the invention, a method ofreducing power consumption in a communications device incorporating aPHY circuit having a normally active multi-channel wideband mode andsingle-channel narrowband mode of operation, the method comprising thesteps of sensing loss of external power to the communications device,requesting to switch to the single-channel narrowband mode of operationand upon approval, shutting down the multi-channel wideband mode ofoperation and activating the single-channel narrowband mode ofoperation.

There is further provided in accordance with the invention, a cablemodem coupled to a cable head-end over a cable network comprising amemory, one or more interface ports, a tuner coupled to a CATV cablehaving a plurality of channels, the tuner operative to tune a receivedbroadband signal in accordance with a tune command, a PHY circuitcoupled to the tuner comprising a wideband analog to digital converter(ADC) and a narrowband ADC, the PHY circuit operative to generate abaseband signal from the output of the tuner, means for reducing powerconsumption of the cable modem in the event of a loss of external powercomprising means for sensing loss of external power to the cable modem,means for requesting from the cable head-end to switch to thesingle-channel narrowband mode of operation, upon approval from thecable head-end, shutting down the multi-channel wideband mode ofoperation and activating the single-channel narrowband mode ofoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrating a cable system incorporating thepower consumption reduction mechanism of the present invention;

FIG. 2 is a block diagram illustrating an example cable modemincorporating the power consumption reduction mechanism of the presentinvention;

FIG. 3 is a block diagram illustrating an example embodiment of thecable modem power consumption reduction mechanism of the presentinvention in more detail;

FIG. 4 is a flow diagram illustrating the external power failureswitching method of the present invention; and

FIG. 5 is a flow diagram illustrating the external power restore methodof the present invention.

DETAILED DESCRIPTION OF THE INVENTION Notation Used Throughout

The following notation is used throughout this document.

Term Definition AC Alternating Current ADC Analog to Digital ConverterAFE Analog Front End ASIC Application Specific Integrated Circuit ATMAsynchronous Transfer Mode CATV Community Antenna Television or Cable TVCM Cable Modem CMTS Cable Modem Termination System CO Central Office CPUCentral Processing Unit DAC Digital to Analog Converter DBC DynamicBonding Change DC Direct Current DHCP Dynamic Host Control ProtocolDOCSIS Data Over Cable Service Interface Specification DSID DownstreamService ID DSL Digital Subscriber Line DSP Digital Signal Processor DVRDigital Video Recorder EEROM Electrically Erasable Read Only Memory EMTAEmbedded Multimedia Terminal Adapter FPGA Field Programmable Gate ArrayGPIO General Purpose I/O HDL Hardware Description Language HFC HybridFiber Coaxial I/O Input/Output IC Integrated Circuit IP InternetProtocol LAN Local Area Network LED Light Emitting Diode MAC MediaAccess Control MPEG Moving Picture Experts Group MSO Multiple ServiceOperator NB Narrowband PC Personal Computer PDA Personal DigitalAssistant PGA Programmable Gain Amplifier POTS Plain Old TelephoneService PSTN Public Switched Telephone Network QAM Quadrature AmplitudeModulation QoS Quality of Service RAM Random Access Memory RF RadioFrequency ROM Read Only Memory SLIC Subscriber Line Interface Card SONETSynchronous Optical Network TV Television USB Universal Serial Bus VoIPVoice over IP WAN Wide Area Network WB Wideband WLAN Wireless Local AreaNetwork

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a novel apparatus and method of reducing thepower consumption of a communications device such as a cable modem. Thereduced power consumption mechanism of the present invention isapplicable to communication systems wherein it is desirable tosignificantly reduce power consumption during battery operation. Themechanism is particularly suitable for use in cable systems adapted toimplement the DOCSIS 3.0 specification which permits the fallback of thecable modem to DOCSIS 2.0 operation whereby operation switches frommulti-channel (i.e. DOCSIS 3.0) to single-channel (i.e. DOCSIS 2.0)operation.

To aid in understanding the principles of the present invention, thedescription is provided in the context of a DOCSIS 3.0 capable cablesystem comprising a cable modem adapted to receive an RF feed from acable head-end (i.e. CMTS) and to distribute video, Internet andtelephony to a subscriber premises. It is appreciated, however, that theinvention is not limited to use with any particular communication deviceor standard and may be used in optical, wired and wireless applications.Further, the invention is not limited to use with a specific technologybut is applicable to any situation where it is desired to reduce thepower consumption during battery operation of the device.

Note that throughout this document, the term communications device isdefined as any apparatus or mechanism adapted to transmit, or transmitand receive data through a medium. The communications device may beadapted to communicate over any suitable medium such as RF, wireless,infrared, optical, wired, microwave, etc. In the case of wirelesscommunications, the communications device may comprise an RFtransmitter, RF receiver, RF transceiver or any combination thereof.

The term cable modem is defined as a modem that provides access to adata signal sent over the cable television infrastructure. The termvoice cable modem is defined as a cable modem that incorporates VoIPcapabilities to provide telephone services to subscribers. Channelbonding is defined as a load-sharing technique for logically combiningmultiple DOCSIS channels into a single virtual pipe. It is described indetail in the DOCSIS 3.0 specification, incorporated herein by referencein its entirety.

Cable System Incorporating Reduced Power Consumption Mechanism

A block diagram illustrating a cable modem system incorporating thereduced power consumption mechanism of the present invention is shown inFIG. 1. The system, generally referenced 10, comprises an operatorportion 11 connected to the public switched telephone network (PSTN) 12and the Internet 14 or other wide area network (WAN), a link portion 13comprising the RF cable 28 and a subscriber portion 15 comprising thesubscriber premises 34.

The operator portion 11 comprises the cable head-end 17 which is adaptedto receive a number of content feeds such as satellite 16, local antenna18 and terrestrial feeds 26, all of which are input to the combiner 24.The cable head-end also comprises the voice over IP (VoIP) gateway 20and Cable Modem Termination System (CMTS) 22. The combiner merges the TVprogramming feeds with the RF data from the CMTS.

The Cable Modem Termination System (CMTS) is a computerized device thatenables cable modems to send and receive packets over the Internet. TheIP packets are typically sent over Layer 2 and may comprise, forexample, Ethernet or SONET frames or ATM cell. It inserts IP packetsfrom the Internet into MPEG frames and transmits them to the cablemodems in subscriber premises via an RF signal. It does the reverseprocess coming from the cable modems. A DOCSIS-compliant CMTS enablescustomer PCs to dynamically obtain IP addresses by acting as a proxy andforwarding DHCP requests to DHCP servers. A CMTS may provide filteringto protect against theft of service and denial of service attacks oragainst hackers trying to break into the cable operator's system. It mayalso provide traffic shaping to guarantee a specified quality of service(QoS) to selected customers. A CMTS may also provide bridging or routingcapabilities.

The subscriber premises 34 comprises a splitter 38, cable appliances 36such as televisions, DVRs, etc., cable modem 40, router 48, PCs or othernetworked computing devices 47 and telephone devices 51. Cable serviceis provided by the local cable provider wherein the cable signaloriginates at the cable head end facility 17 and is transmitted over RFcable 28 to the subscriber premises 34 where it enters splitter 38. Oneoutput of the splitter goes to the televisions, set top boxes, and othercable appliances via internal cable wiring 37.

The other output of the splitter comprises the data portion of thesignal which is input to the cable modem 40. The cable modem is adaptedto provide both Ethernet and USB ports. Typically, a router 48 isconnected to the Ethernet port via Ethernet cable 54. One or morenetwork capable computing devices 47, e.g., laptops, PDAs, desktops,etc. are connected to the router 48 via internal Ethernet network wiring46. In addition, the router may comprise or be connected to a wirelessaccess point that provides a wireless network (e.g., 802.11b/g/a)throughout the subscriber premises.

The cable modem also comprises a subscriber line interface card (SLIC)42 which provides the call signaling and functions of a conventionallocal loop to the plurality of installed telephone devices 51 viainternal 2-wire telephone wiring 52. In particular, it generates callprogress tones including dial tone, ring tone, busy signals, etc. thatare normally provided by the local loop from the CO. Since the telephonedeices 51 are not connected to the CO, the SLIC in the cable modem mustprovide these signals in order that the telephone devices operatecorrectly.

The cable modem also comprises the reduced power consumption mechanism44 of the present invention. The power line detector is operative tosense an external power source failure and switch to battery operationwhich includes switching operation of the cable modem PHY frommulti-channel (DOCSIS 3.0) operation to single-channel (DOCSIS 2.0)operation, as described in more detail infra.

Voice Cable Modem Incorporating Reduced Power Consumption Mechanism

A block diagram illustrating an example cable modem incorporating thereduced power consumption mechanism of the present invention is shown inFIG. 2. The cable modem, generally referenced 60, comprises a diplexer89, tuner 64, analog front end (AFE) circuit 65, DOCSIS PHY circuit 66incorporating a reduced power consumption block 67, DOCSIS compatibleprocessor 74 incorporating the reduced power consumption block 83 withinthe DOCSIS MAC 88, VoIP processor 75, voice codec 77, subscriber lineinterface card (SLIC) 79, phone port 81, antenna 61, wireless local areanetwork (WLAN) 63, Ethernet interface 76, Ethernet LAN port 78, generalpurpose (I/O) (GPIO) interface 80, LEDs 82, universal serial bus (USB)interface 84, USB port 86, AC adapter 71, power management circuit 73,ROM 68, RAM 70 and FLASH memory 72. Note that in the example embodimentpresented herein, the cable modem and DOCSIS enabled processor 74 areadapted to implement the DOCSIS 3.0 standard which provides for channelbonding wherein multiple downstream channels are used to transmit datafrom the CMTS to the cable modem. A plurality of contexts may beestablished whereby packets are sent over multiple downstream channelsand recombined at the cable modem to yield several separate contexts.

In operation, the cable modem processor 74 is the core chip set which inthe example presented herein comprises a central single integratedcircuit (IC) with peripheral functions added. Depending on theimplementation, one or more of the functions shown external to theprocessor may be implemented within the processor without departing fromthe scope of the invention. For example, the AFE and PHY circuits may beimplemented within the processor integrated circuit (IC) 74.

The voice over IP (VoIP) processor 75 implements a mechanism to providephone service outside the standard telco channel. Chipset DSPs andcodecs 77 add the functionality of POTS service for low rate voice data.

The cable modem also comprises a subscriber line interface card (SLIC)79 which functions to provide the signals and functions of aconventional local loop to a plurality of telephone devices connectedvia the phone port 81 using internal 2-wire telephone wiring. Inparticular, it generates call progress tones including dial tone, ringtone, busy signals, etc. that are normally provided by the local loopfrom the CO. Since the telephone deices are not connected to the CO, theSLIC in the cable modem must provide these signals in order that thetelephone devices operate correctly.

In a traditional analog telephone system, each telephone or othercommunication device (i.e. subscriber unit) is typically interconnectedby a pair of wires (commonly referred to as tip and ring or together assubscriber lines, subscriber loop or phone lines) through equipment to aswitch at a local telephone company office (central office or CO). Atthe CO, the tip and ring lines are interconnected to a SLIC whichprovides required functionality to the subscriber unit. The switches atthe central offices are interconnected to provide a network of switchesthereby providing communications between a local subscriber and a remotesubscriber.

The SLIC is an essential part of the network interface provided toindividual analog subscriber units. The functions provided by the SLICinclude providing talk battery (between 5 VDC for on-hook and 48 VDC foroff-hook), ring voltage (between 70-90 VAC at a frequency of 17-20 Hz),ring trip, off-hook detection, and call progress signals such asringback, busy, and dial tone.

A SLIC passes call progress tones such as dial tone, busy tone, andringback tone to the subscriber unit. For the convenience of thesubscriber who is initiating the call, these tones normally provided bythe central office give an indication of call status. When the callingsubscriber lifts the handset or when the subscriber unit otherwisegenerates an off hook condition, the central office generates a dialtone and supplies it to the calling subscriber unit to indicate theavailability of phone service. After the calling subscriber has dialed aphone number of the remote (i.e. answering) subscriber unit, the SLICpasses a ring back sound directed to the calling subscriber to indicatethat the network is taking action to signal the remote subscriber, i.e.that the remote subscriber is being rung. Alternatively, if the networkdetermines that the remote subscriber unit is engaged in another call(or is already off-hook), the network generates a busy tone directed tothe calling subscriber unit.

The SLIC also acts to identify the status to, or interpret signalsgenerated by, the analog subscriber unit. For example, the SLIC provides−48 volts on the ring line, and 0 volts on the tip line, to thesubscriber unit. The analog subscriber unit provides an open circuitwhen in the on-hook state. In a loop start circuit, the analogsubscriber unit goes off-hook by closing, or looping the tip and ring toform a complete electrical circuit. This off-hook condition is detectedby the SLIC (whereupon a dial tone is provided to the subscriber). Mostresidential circuits are configured as loop start circuits.

Connectivity is provided by a standard 10/100/1000 Mbps Ethernetinterface 76 and Ethernet LAN port 78, USB interface 84 and USB port 86or with additional chip sets, such as wireless 802.11a/b/g via WLANinterface 63 coupled to antenna 61. In addition, a GPIO interface 80provides an interface for LEDs 82, etc. The network connectivityfunctions may also include a router or Ethernet switch core. Note thatthe DOCSIS MAC 88 and PHY 66 are typically integrated into the cablemodem processor 74 or may be separate as shown in FIG. 2 wherein theDOCSIS PHY circuit 66 is shown separate from the processor 74.

In the example embodiment presented herein, the diplexer 89 is coupledto the CATV signal from the CMTS via port 62 and is operative to coupledthe receive and transmit signals to the CATV cable. The tuner 64 isoperative to convert the RF signal received over the RF cable to an IFfrequency in accordance with a tune command received from the processor.

The cable modem 60 comprises a processor 74 which may comprise a digitalsignal processor (DSP), central processing unit (CPU), microcontroller,microprocessor, microcomputer, ASIC, FPGA core or any other suitableprocessing means. The cable modem also comprises static read only memory(ROM) 68, dynamic main memory 70 and FLASH memory 72 all incommunication with the processor via a bus (not shown).

The magnetic or semiconductor based storage device 68 (i.e. RAM) is usedfor storing application programs and data. The cable modem comprisescomputer readable storage medium that may include any suitable memorymeans, including but not limited to, magnetic storage, optical storage,semiconductor volatile or non-volatile memory, biological memorydevices, or any other memory storage device.

Software adapted to implement the reduced power consumption mechanism ofthe present invention is adapted to reside on a computer readablemedium, such as a magnetic disk within a disk drive unit. Alternatively,the computer readable medium may comprise a floppy disk, removable harddisk, Flash memory 72, EEROM based memory, bubble memory storage, ROMstorage 70, distribution media, intermediate storage media, executionmemory of a computer, and any other medium or device capable of storingfor later reading by a computer a computer program implementing thesystem and methods of this invention. The software adapted to implementthe reduced power consumption mechanism of the present invention mayalso reside, in whole or in part, in the static or dynamic main memories68 or in firmware within the processor of the computer system (i.e.within microcontroller, microprocessor or microcomputer internalmemory).

A block diagram illustrating an example embodiment of the cable modempower consumption reduction mechanism of the present invention in moredetail is shown in FIG. 3. The portion of the cable modem circuit shownin more detail, generally referenced 90, comprises a diplexer 94 coupledto the CATV cable 92, tuner 96 comprising a wideband filter 98 such asan LC filter and a narrowband filter 100 such as a surface acoustic wave(SAW) filter, analog front end (AFE) circuit 102 comprising a widebandanalog to digital converter (ADC) 108 and narrowband ADC 110, PHYcircuit 104, MAC 106, power supply control 112 coupled to an externalpower source 114, battery 116, wideband/narrowband (WB/NB) controlcircuit 118, digital to analog converter (DAC) 120, image reject filter124, programmable gain amplifier (PGA) 126 and PGA control circuit 122.

The mechanism of the present invention enables the use of a singlewideband tuner and single wideband ADC during normal operation (i.e.using external power source). During battery mode operation, thewideband ADC, which has higher power consumption, is shut down and anarrowband ADC is activated in its place.

During operation on external power, the wideband ADC in the PHY is usedin the receive path. The wideband ADC is capable of supportingmulti-channel DOCSIS 3.0 operating bandwidth of 64 MHz (or more). Thecurrent consumption during this mode is relatively high but is not muchof a concern due to the fact that power is supplied from an externalsource, typically the AC mains utility power.

During a power failure, however, depending on the location, the cablemodem is required to continue to provide VOIP telephony services andsupport to allow users to make telephone calls during a power failure.The cable modem must support VOIP for a defined finite time period, suchas 8 hours. In order to meet this requirement, in accordance with theinvention, the WB/NB control 118 in the cable modem switches frommulti-channel to single-channel operation. This permits the shuttingdown of the high power consuming circuitry such as the wideband ADC 108in the AFE. In its place, the WB/NB control circuit activates thenarrowband ADC 110 which consumes significantly less power. Furtherreductions in power consumption are achieved by configuring the PGA 126to draw less current.

The external power failure switching method of the invention will now bedescribed in more detail. A flow diagram illustrating the external powerfailure switching method of the present invention is shown in FIG. 4.With reference to FIGS. 3 and 4, the power supply control circuit 112functions to sense the loss of external power source 114 (step 130).This is achieved using any suitable technique well-known in the art. Thepower supply circuit informs the MAC 106 or other entity in the cablemodem via signaling or other means that external power has been lost(step 132).

In response, the MAC or other suitable entity on the processor generatesa message to the cable head-end (i.e. to the CMTS) indicating that dueto the occurrence of a power failure, it is requesting to switch toDOCSIS 2.0 single-channel mode operation (step 134). For example, theDOCSIS 3.0 standard CM-STATUS message with event type code set to ‘9’can be used to request this switch from the CMTS. Table 1 below providesthe relevant portions of Table 6-55 Event Type Codes from Section6.4.34.2 of the standard specification.

TABLE 1 Portion of Table 6-55 Event Type Codes from DOCSIS 3.0Specification Status Report Events Parameters Reported Event Type CodeTrigger Event to Trigger Event to Downstream Upstream Event Condition‘on’ ‘off’ Channel ID Channel ID DSID 9 CM CM detects loss CM detectsthe N/A N/A N/A operating on of A/C Power for presence of A/C batterymore than 5 Power and has backup seconds and the returned from CM isoperating backup battery on battery to operating on backup. A/C power.10 CM returned CM detects the CM detects loss N/A N/A N/A to A/Cpresence of A/C of A/C Power power Power for more and the CM is then 5seconds operating on and has returned battery backup. from backupbattery to operating on A/C power.

Note that the cable modem (CM) power events 9 and 10 presented in Table1 above are only applicable to cable modems with battery backupcapability. These events are used by the cable modem to signal the CMTSwhen the cable modem is operating on battery power. If the CMTS receivesa CM-STATUS message with “CM operating on battery backup” indicated, theCMTS sends a dynamic bonding change (DBC) message to the cable modem toreduce the cable modem operation to a single upstream and singledownstream channel. This functions to prevent shortened battery life ifcable modem operation is left in multi-channel transmission andreception.

In response to the CM-STATUS message, the CMTS switches to DOCSIS 2.0operation for the requesting cable modem and replies with an approval(step 136). Upon receiving an approval, the WB/NB control in the cablemodem signals the PHY/AFE to switch from wideband to narrowbandoperation with respect to the tuner, AFE and PHY circuits (step 138). Inparticular, the WB/NB control circuit is operative to shut down thewideband ADC and activate the narrowband ADC thus greatly reducing powerconsumption. Since the cable modem is communicating to the CMTS over asingle channel, the wideband ADC needed for multi-channel operation isnot necessary. Further, the tuner is configured to use the complementarynarrowband SAW filter rather than the wideband LC filter (step 140).

To further reduce power consumption, the PGA control circuit 122 reducesthe current consumption of the PGA which results in reduced linearity ofthe amplifier 126. The reduction in linearity, however, is tolerableconsidering the narrowband communications (i.e. single-channel) betweenthe cable modem and the CMTS. Thus, by controlling the linearity of thePGA during single channel DOCSIS 2.0 operation, further reductions inpower consumption are achieved.

The external power restore method of the invention will now be describedin more detail. A flow diagram illustrating the external power restoremethod of the present invention is shown in FIG. 5. With reference toFIGS. 3 and 5, at some point later in time the power supply controlcircuit 112 senses that external power 114 has been restored (step 150).The power supply control circuit signals the MAC accordingly (step 152)and a message is generated and sent to the CMTS in the cable head-endindicating that external power has been restored and the cable modem isrequesting to switch back to DOCSIS 3.0 multi-channel operation (step154). In the context of DOCSIS 3.0, a CM-STATUS message with Event TypeCode set to 10, as shown in Table 1 presented supra, is sent to theCMTS.

In response, the CMTS returns to DOCSIS 3.0 operation for the requestingcable modem and replies with an approval (step 156). Upon receiving theapproval, the MAC or other suitable entity, signals the WB/NB controlcircuit 118 to switch back to wideband operation (step 158). The WB/NBcontrol circuit signals the tuner, AFE and PHY circuits to switch tonarrowband operation (step 160). In particular, the narrowband ADC isshutdown and the wideband ADC is activated. Further, the tuner isconfigured to use the wideband filter 98 rather than the narrowbandfilter 100 (step 162).

It is intended that the appended claims cover all such features andadvantages of the invention that fall within the spirit and scope of thepresent invention. As numerous modifications and changes will readilyoccur to those skilled in the art, it is intended that the invention notbe limited to the limited number of embodiments described herein.Accordingly, it will be appreciated that all suitable variations,modifications and equivalents may be resorted to, falling within thespirit and scope of the present invention.

1. A method of reducing power consumption in a cable modem coupled to acable head-end and incorporating a PHY circuit having a normally activemulti-channel wideband mode and single-channel narrowband mode ofoperation, said method comprising the steps of: sensing loss of externalpower to said cable modem; requesting from said cable head-end to switchto said single-channel narrowband mode of operation; and upon approvalfrom said cable head-end, shutting down said multi-channel wideband modeof operation and activating said single-channel narrowband mode ofoperation by configuring a tuner circuit to switch to a narrow bandintermediate frequency (IF) channel utilizing a surface acoustic wave(SAW) filter circuit.
 2. The method according to claim 1, wherein saidstep of activating said single-channel narrowband mode of operationcomprises the steps of: shutting down a wideband analog to digitalconverter (ADC) circuit; and activating a narrowband ADC circuit.
 3. Themethod according to claim 1, wherein said single-channel narrowband modeof operation comprises Data Over Cable Service Interface Specification(DOCSIS) 2.0 single-channel operation.
 4. The method according to claim1, wherein said multi-channel wideband mode of operation comprises DataOver Cable Service Interface Specification (DOCSIS) 3.0 multiple channeloperation.
 5. The method according to claim 1, wherein said step ofrequesting comprises sending a Data Over Cable Service InterfaceSpecification (DOCSIS) 3.0 CM-STATUS message to a cable modemtermination system (CMTS) indicating a loss of external power.
 6. Themethod according to claim 1, wherein said step of activating comprisesthe step of lowering a sampling clock rate of an analog to digitalconverter (ADC).
 7. An apparatus for reducing power consumption in acable modem coupled to a cable modem termination service (CMTS),comprising: a power supply control circuit coupled to an external powersource and a battery, said power supply control circuit operative tosense a failure of said external power source and switch to batterybackup; an analog front end (AFE) circuit comprising a wideband analogto digital converter (ADC) and a narrowband ADC; and awideband/narrowband (WB/NB) control circuit operative to receive anindication of a loss of external power from said power supply circuitand to shut down said wideband ADC and activate said narrowband ADC inresponse thereto, wherein said WB/NB control circuit further comprisesmeans for configuring a tuner circuit coupled to said AFE to switch to anarrow band intermediate frequency (IF) channel utilizing a surfaceacoustic wave (SAW) filter circuit in the event of a loss of externalpower.
 8. The apparatus according to claim 7, wherein said WB/NB controlcircuit is operative to shut down said wideband ADC and activate saidnarrowband ADC upon approval from said CMTS.
 9. The apparatus accordingto claim 7, wherein said narrowband ADC is used during Data Over CableService Interface Specification (DOCSIS) 2.0 single-channel operation.10. The apparatus according to claim 7, wherein said wideband ADC isused during Data Over Cable Service Interface Specification (DOCSIS) 3.0multiple channel operation.
 11. The apparatus according to claim 7,wherein said WB/NB control circuit is operative to lower a samplingclock rate of an analog to digital converter (ADC) circuit within saidAFE in the event of a loss of external power.
 12. A method of reducingpower consumption in a cable modem coupled to a cable head-end andincorporating a PHY circuit having a normally active multi-channelwideband mode and single-channel narrowband mode of operation, saidmethod comprising the steps of: switching from said multi-channelwideband mode of operation to said single-channel narrowband mode ofoperation in response to sensing a loss of external power to said cablemodem; configuring a tuner circuit to switch to a narrow bandintermediate frequency (IF) channel utilizing a surface acoustic wave(SAW) filter circuit; and switching from said single-channel narrowbandmode of operation back to said multi-channel wideband mode of operationin response to sensing the restoration of external power to said cablemodem.
 13. The method according to claim 12, comprising the steps of:shutting down a wideband analog to digital converter (ADC) circuit; andactivating a narrowband ADC circuit.
 14. The method according to claim12, wherein said step of switching from said single-channel narrowbandmode of operation back to said multi-channel wideband mode of operationcomprises the steps of: configuring the tuner circuit to switch to awideband intermediate frequency (IF) channel; shutting down a narrowbandanalog to digital converter (ADC) circuit; and activating a wideband ADCcircuit.
 15. The method according to claim 12, wherein saidsingle-channel narrowband mode of operation comprises Data Over CableService Interface Specification (DOCSIS) 2.0 single-channel operation.16. The method according to claim 12, wherein said multi-channelwideband mode of operation comprises Data Over Cable Service InterfaceSpecification (DOCSIS) 3.0 multiple channel operation.
 17. The methodaccording to claim 12, wherein said step of requesting comprises sendinga Data Over Cable Service Interface Specification (DOCSIS) 3.0 CM-STATUSmessage to a cable modem termination system (CMTS) indicating a loss ofexternal power.
 18. The method according to claim 13, wherein said stepof activating comprises the step of lowering a sampling clock rate of ananalog to digital converter (ADC).
 19. A method of reducing powerconsumption in a communications device incorporating a PHY circuithaving a normally active multi-channel wideband mode and single-channelnarrowband mode of operation, said method comprising the steps of:sensing loss of external power to said communications device; requestingto switch to said single-channel narrowband mode of operation; and uponapproval, shutting down said multi-channel wideband mode of operationand activating said single-channel narrowband mode of operation; andconfiguring a tuner circuit to switch to a narrow band intermediatefrequency (IF) channel utilizing a surface acoustic wave (SAW) filtercircuit.
 20. The method according to claim 19, further comprising thesteps of: sensing the restoration of external power to saidcommunications device; requesting to switch to said multi-channelwideband mode of operation; and upon approval, shutting down saidsingle-channel narrowband mode of operation and activating saidmulti-channel wideband mode of operation.
 21. A cable modem coupled to acable head-end over a cable network, comprising: a memory; one or moreinterface ports; a tuner coupled to a CATV cable having a plurality ofchannels, said tuner operative to tune a received broadband signal inaccordance with a tune command; a PHY circuit coupled to said tunercomprising a wideband analog to digital converter (ADC) and a narrowbandADC, said PHY circuit operative to generate a baseband signal from theoutput of said tuner; a programmable gain amplifier (PGA) in an upstreampath; means for reducing power consumption of said cable modem in theevent of a loss of external power operative to decrease the currentconsumption of said PGA thereby reducing its linearity resulting in areduction in power consumption of said cable modem, said means forreducing power consumption comprising: means for sensing loss ofexternal power to said cable modem; means for requesting from said cablehead-end to switch to said single-channel narrowband mode of operation;upon approval from said cable head-end, shutting down said multi-channelwideband mode of operation and activating said single-channel narrowbandmode of operation.
 22. The cable modem according to claim 21, whereinsaid means for reducing power consumption further comprises: means forsensing the restoration of external power to said cable modem; means forrequesting to switch to said multi-channel wideband mode of operation;and means for upon approval, shutting down said single-channelnarrowband mode of operation and activating said multi-channel widebandmode of operation.
 23. The cable modem according to claim 21, whereinsaid tuner comprises a wideband intermediate frequency (IF) channel anda narrowband IF channel wherein said step of activating comprisesconfiguring said tuner to use said narrowband IF channel.